1. Field of the Invention
This invention relates to a camera of the kind having a movable mirror.
2. Description of the Related Art
The movable mirror arrangement of the recent single-lens reflex cameras generally includes a main mirror and a sub-mirror for automatic focusing. The main mirror is arranged to reflect the light of a photographed object toward a viewfinder optical system. The sub-mirror is arranged to reflect a part of the object light toward a focus detecting device after it has passed through the main mirror.
Many of the movable mirrors recently proposed are arranged to have the sub-mirror movable relative to the movable main mirror. The sub-mirror is urged by a spring to open to permit focus detection when the main mirror is moved down to its finder-viewing position. The sub-mirror is closed to its exposure position when the main mirror is moved up to its exposure position.
A camera using a toggle spring as the spring for urging the sub-mirror was proposed by U.S. Pat. No. 4,320,945. However, the conventional sub-mirror urging device using the toggle spring has imposed many restrictions on design work as it necessitates: The provision of a stopper near an area where an object light flux passes in taking a shot for the purpose of restricting the degree of opening angle of the sub-mirror in its focus detecting position, i.e., in its state of being opened relative to the main mirror; and some arrangement to prevent the light flux from being eclipsed through a space where the stopper is located. The conventional device also has necessitated some arrangement against the adverse effect of inner surface reflection resulting from the provision of the stopper.